Quantum physics is a branch of physics that is bananas and also bonkers.
Once upon a time there was a time when nothing was quantised. This was maybe at the time your grandmother lived, or maybe even before her time. Who's to say? At that time, it was the time when everything was waves.
Planck did his work and he did it well. And then there was quantisation. Plank's work demonstrated that not everything was only comprised of waves, but that some things were also comprised of quanta.
If this is confusing to you, then you can try to squint hard while rereading the above.